This specification refers to bipolar semiconductor devices including a diode structure, in particular to power semiconductor devices, and a manufacturing method therefor.
Diode structures are desired to have a very good surge current strength and also a sufficient dynamic robustness. Moreover, the losses occurring during operation are to be kept small. For this purpose, CAL diodes (CAL=Controlled Axial Lifetime) and EMCON diodes (EMCON=Emitter Controlled) have been developed. In the case of CAL diodes, a heavily doped p-type emitter is used, but the latter additionally requires intensive helium irradiation and further methods for reducing the charge carrier lifetime in order that the turn-off losses do not become too high. EMCON diodes, by contrast, have a relatively weakly p-doped emitter. However, a reduced surge current strength is observed in this case.
A further diode variant is the “speed diode” (self-adjusted p-emitter efficiency diode). While the forward current of this diode essentially flows via a weakly p-doped zone during normal operation, in the surge current case charge carriers are injected from highly p-doped zones and contribute to a high surge current strength and surge energy capacity, respectively. However, the dynamic robustness of the known speed diode is often unsatisfactory.